No ISIS. If we hadn’t ever gone into Iraq to begin with, ISIS wouldn’t exist today.

Significantly smaller US debt. The Bush tax cuts and the Iraq War led to a huge debt. Whether or not Gore would have sent us into Iraq, he would not have enacted Bush’s tax cuts.

Possibly no 2008 financial crisis. Blame for the 2008 financial crisis falls on many: including Congress, the Federal Reserve, and Bill Clinton. The Bush Administration, however, holds much of the blame. Bush’s general contempt for regulation and the culture that created, along with his tendency to appoint people to important positions without the necessary expertise, were among several causes of the crisis. Even if the crisis had occurred under Gore, a lower debt would have allowed us to handle it more easily. This one crisis destroyed tens of trillions of dollars of wealth.

About a million other, less important things would be better (and admittedly many would be worse), including more investments in science, better gun control, etc.

The effects of one bad president are tremendous. Due to the scale of the US Government, a marginal improvement still has a huge effect.

With an annual budget of close to $4T, even a 2% increase in efficiency of the US Government would mean almost a trillion dollars of value over 10 years – or about the same value as the combined market caps of Microsoft and Facebook.

But the effects of Presidents are much longer lasting than a decade. FDR’s New Deal was instituted to immediately relieve poverty, but it still forms the basis of many of our social safety nets today. Andrew Johnson’s failures during Reconstruction (150 years ago) after the assassination of Lincoln can still be felt in racial tensions today.

This Election

This election could be the most important in US history.

Here is a short list of just some of the major problems a Trump Presidency might lead to:

Trump could upend our entire democracy. If Trump wins the presidency, Republicans will also control both houses of Congress. The Republican Senate could entirely eliminate the filibuster, thus giving themselves a supermajority. Trump will get at least one Supreme Court pick. At this point, Republicans would completely control all three branches of government. That’s when things could go from bad to worse. Republicans have been afraid of trying to stop Trump, even before he was the nominee. Trump has already demonstrated a habit of attacking Republicans who only half-heartedly support him. Imagine the fear they’d feel when he was President and additionally in charge of the FBI, CIA, NSA, and Justice Department. With Trump as President, Republican congressmen would by and large green light his agenda. Trump has indicated this agenda includes opening up “libel laws” to censor the free press, and he has encouraged voter intimidation of Democratic leaning minorities. If Republicans in Congress wanted, they could even increase the number of Supreme Court Justices or impeach justices they disagreed with, achieving an even more sympathetic court. By controlling the press and who can vote, Trump could enable the Republicans to pick up legislative seats in the elections of 2018, 2020, and 2022, specifically helping those loyal to him. Each election could lead to a more extreme pro-Trump Congress, which could pass more extreme laws, allowing for even more gains. Imagine laws requiring an intimidating police force at largely minority polling places to “make sure the election isn’t rigged.” At this point, with the the executive, legislative, and judicial branches (and likely the press and electorate) full of people who thought like, were loyal to, or fearful of Trump, America would look like Russia. If Trump wanted to extend his presidency past the two term limit, Republicans would conceivably have enough seats in the legislature to amend the constitution, eliminating the term limit. Remember, this is a man who has no respect for democracy, and even once said he’d accept the democratic result of the election – “if I win.”

Conventional wisdom holds that no single vote can sway the election. But that is not true. Academic research indicates each vote in a swing state has about a 1 in 10 million chance of swaying the election. For comparison, that’s about the chance of rolling the same number on a 6-sided die 10 times in a row – an unlikely occurrence for sure, but one which is still plausible.

Back of the envelope calculations with simple assumptions agree with this estimate. Imagine a fictitious swing state which has 20 electoral votes from 5 million votes cast. Let’s assume the outcome of the election within our swing state will be within 5% of a tie, but that we have absolutely no idea who will win the state or by how much within that range. That tells us that the results for the vote difference between the candidates in this state have a range of 500,000 votes. Your vote is meaningful only if it is the actual swing vote for the state, which is thus expected with probability 1 in 500,000.

But the state is only important if your candidate would have had fewer than 270 electoral votes without your state (probability around 1/2) and only by less than the number of electoral votes associated with your state (around 1/5 here, assuming some random electoral outcome between 170 and 269). Even though Clinton is the favorite to win the current election, if she does lose, it will likely be within 20 electoral votes. Therefore the total 1 in 10 chance of losing by 20 electoral votes is a reasonable estimate.

Multiplying all the probabilities together gives a 1 in 5 million chance of your one vote changing the entire election, within the ballpark of the original 1 in 10 million figure.

To recap how important this election is, the effects of this election going one way or the other appear to include:

on the order of trillions of dollars of wealth

at least several years improvements in the lives of on the order of 1 billion people in the world (including hundreds of millions of Americans)

probably at least a few percent difference in human extinction or total civilization collapse (from global warming, WWIII, or some later action that an America turned to fascism may take)

Multiplying these effects by the chance of your vote swaying the election (1 in 10 million) gives the expected value of your vote.

The cost of voting is the one hour or so that it takes, for which you create expected value of hundreds of thousands of dollars of wealth, improvements to the lives of hundreds of people including tens of Americans, and a minuscule but still positive effect on decreasing the chance of human extinction.

Even if one is cynical and believes that a close enough race will lead a judicial or legislative body to make the eventual decision, either explicitly or through a questionable recount, your one vote can still be the difference between the race being considered “close enough” for this body to make such a decision or not. This exact case happened in the 1839 Massachusetts gubernatorial election, where Marcus Morton won 51,034 out of 102,066 votes. A majority was needed to win; if he had received 1 fewer vote, a simple plurality would have sent the decision to the state legislature that was of an opposing political party.

Elections have been decided by a single vote, and while the chances of a single vote swaying the Presidential election are small, each vote in a swing state does have the possibility of swaying the entire election. Due to the scale of the US government, combined with the special threats that Donald Trump presents, the expected value from each of these votes is immense.